The present invention pertains to a device for correcting a characteristic error of a camera. More particularly, the present invention pertains to a camera characteristic errors correcting device capable of correcting an error of specific data expressible by rectangular coordinate axes.
A camera is typically provided with photometric/range-finding ICs and motor drive ICs used for auto-diaphragming, lens driving and film feeding. Accommodated in a camera box body is an electrical unit incorporating a program for executing a variety of photographing modes together with a CPU for controlling the ICs.
For attaining high multifunctions by means of a program AE and a program AF while improving the operability of the camera, the CPU is constructed of a 1-chip microcomputer incorporating analog input terminals, a ROM, a RAM and A/D converting circuits. The CPU performs additional functions such as monitoring battery capacity and voltage, synchro-flashing, adjustments of variations in inside and outside temperatures of the camera box body, as well as display control of a liquid crystal display unit, LEDs and so forth.
Adjustment of the camera before initial use does not typically require the preparation of multiple theoretical characteristic data according to the type of devices, lots, and delivery districts, provided some redundant data are added to the theoretical characteristic data. However, as automation of cameras advances and built-in programs and data increase (for example, lens characteristic, lens mounting positions and characteristics of a light-receiving element, light-emitting element and temperature sensor), adjustment before initial use can not be accomplished effectively using only one kind of data corresponding thereto. Problems occur because unifiable data are put in the high-order, while ununifiable data are hierachized. To achieve a commercial success, typically such a camera is arranged for dedicated use.
A great majority of cameras operate based on the theoretical characteristic data. An example is a distance detecting device disclosed in Japanese Patent Laid-Open Publication No. 198818/1988, in which an error coefficient for the theoretical characteristic data is measured at the time of delivery of the camera. This error coefficient is stored in the storage unit to correct the characteristic error.
However, the range-finding factors do not necessarily exhibit rectilinear characteristics due to the following items.
(1) Influence of electric noises: PA1 (2) The reflected light is incident on a portion other than a normal position due to an influence of lens aberration or the like. PA1 (3) The ratio deviates when the characteristics of the light-receiving sensor are not uniform. PA1 (4) The incident position to a PSD deviates due to an influence of roughness on the mold surface of the light-receiving sensor. PA1 (5) The incident position deviates on account of a curvature of a plastic cover for covering the front surface of the light projecting/receiving lens.
If the subject being photographed exists at a remote position, variations in magnitudes of signals and noises are small because less amount of light is reflected therefrom.
For these reasons, range-finding with a high accuracy cannot be expected, and applicability to a high grade high performance camera cannot be obtained.
In an electric adjusting device of a camera which is disclosed in Japanese Patent Laid-Open Publication No. 25733/1987, the data are not hierachized, and the programs are not subroutinized. Written to a nonvolatile memory (hereinafter referred to as an E.sup.2 PROM) is a measured error (.DELTA.Tv) for each of a series of camera units with respect to an exposure time Tv calculated from, e.g., an aperture value Av, a film sensitivity Sv and a brightness Bv without using the theoretical characteristic data. The characteristic error is corrected based on this measured error .DELTA.Tv.
This method, however, presents several drawbacks. A large capacity E.sup.2 PROM is needed. In addition, the number of testing steps (including a write time of the E.sup.2 PROM) for measurement increases, and the costs of producing the camera is high.